1. Field of the Invention
The present invention relates to a color signal processing apparatus and method, and more particularly, to a color signal processing apparatus and method for calculating a control vector which is a driving signal for a multi-primary display (MPD) corresponding to an input color signal so that the input standard color signal is reproduced on the MPD using four or more primary colors.
2. Description of the Related Art
In general, color-reproducing devices such as monitors, scanners, printers, and so on, employ a different color space from one other according to their respective utilization areas, in which the color space is referred to as a method representing relations of a certain color with the other colors, that is, a method defining colors. Such color spaces include the RGB color space employed for color CRT monitors, computer graphic devices, and so on, the CMY color space for color image printing devices and the like, and the HSI color space for devices dealing with hue, saturation, and intensity, respectively. Further, there are the CIE color spaces used for defining device-independent colors which can precisely reproduce colors in any device, and the CIE color spaces typically include the CIE-XYZ color space, CIE L*a*b color space, CIE L*u*v color space, and so on.
In the meantime, the color-reproducing devices have different kinds of colors depending upon a color space used therefor, but, in general, use the basic three primary colors. That is, the three primary colors of red, green, and blue mixed with one another are used in the case that the RGB color space is used, and the three primary colors of cyan, magenta, and yellow are used in the case of the CMY color space.
Recently, there has been an attempt to stretch a color gamut by using four or more primary colors in color-reproducing devices, for an example of which there is a multi-primary display (MDP). The MPD refers to a display system using four or more primary colors to stretch a color gamut, that is, to extend a color-reproducing range more than the three-channel display system using the existing three primary colors. In order to reproduce a standard color signal using the three primary colors in such an MPD, there needs to be a color signal processing device for calculating a control vector, which is a driving signal of the MPD in correspondence to an input color signal.
FIG. 1 is a block diagram for showing an example of a conventional color signal processing apparatus. In FIG. 1, the conventional color signal processing apparatus has a color signal conversion unit 10, a 2D-LUT memory 20, a matrix coefficient selection unit 30, and a matrix processing unit 40.
The color signal conversion unit 10 converts the input color signal into an xy color signal in the CIE-XYZ color space. The xy color signal converted in the color signal conversion unit 10 is inputted in the 2D-LUT memory 20. As shown in FIG. 2, stored in the 2D-LUT memory 20 is 2D-LUT data corresponding to a range of the color gamut of the input color signal, and the 2D-LUT data is transferred to the matrix coefficient selection unit 30, and then a matrix coefficient corresponding to the color gamut is calculated. The matrix coefficient calculated in the matrix coefficient selection unit 30 is transferred to the matrix processing unit 40, and a control vector CL corresponding to the input color signal is outputted through vector processing procedures as shown in FIG. 3. Here, in a polyhedron corresponding to a color gamut of an MPD as shown in FIG. 4, each area shown in FIG. 2 corresponds to a boundary area of all the color gamut capable of belonging to every plane of a polyhedron excluding a black point b when the black point b forms a vertex, that is, a pyramid including a plane formed when four vertices are connected.
However, there exists a problem in that such a conventional method requires the 2D-LUT data to be calculated in advance according to the characteristics of every system for a corresponding matrix coefficient selection and a 2D-LUT memory is needed to store the 2D-LUT data. Further, there exists a problem in that quantization errors may occur during a process for calculating the 2D-LUT data, and the 2D-LUT memory should be so large enough in size that a corresponding matrix coefficient can be selected without errors at boundaries of a corresponding area.